Comparison of broth micro dilution and disk diffusion methods for susceptibility testing of dermatophytes

Background: Dermatophytes are responsible for the majority of the fungal infections involving skin, hair and nails. There has been a remarkable increase in the number of fungal infections especially in those people whose immune system is compromised by aging, HIV infection, organ transplantation or cancer therapy

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Objective: The aim of this study was to compare both broth microdilution method and disk diffusion method for in-vitro activity of some antifungal drugs [Terbinafine, Fluconazole, Itraconazole] against different species of dermatophytes

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Patients and Method: This study was performed on 50 dermatophyte isolates recovered from various clinical specimens [skin, hair and nail] collected from dermatology outpatient clinic of Ain Shams University Hospital. All samples were cultured on sabarouds. Isolates recovered from SDA were subcultured on Potato Dextrose Agar [PDA] and incubated at 28 degree C for 7 days to enhance sporulation. The growth was harvested in sterile saline and the conidial and hyphal suspension was adjusted to 0.5 macfarland. Then antifungal susceptibility was done using: Disk diffusion [DD] method and Broth micro dilution [BMD] method

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Results: There was a highly significant agreement between the antifungal susceptibility testing of fluconazole, itraconazole and terbinafine by disk diffusion method and Broth micro-dilution method. In our study agreement between both methods for itraconazole was 1.00 [kappa], for terbinafine was 0.947, and for fluconazole was 0.878. The factors that may affect the results of BMD or DD are type and size of inoculum, composition of the media, temperature and duration of incubation and disc strength

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Conclusion: There was a highly significant agreement between the antifungal susceptibility testing of fluconazole, itraconazole and terbinafine by disk diffusion method and Broth micro-dilution method